When will my order discussed in the previous email be manufactured and available for shipping?
When will you be able to manufacture and ship my order discussed in the previous email?
解答1と解答2のように一つの長い文章で言えますが、分けて言った方がいいかもしれません。例えば “I have a question about the order discussed in my previous email. When do you think it will be manufactured and shipped?” (前回メールした注文について質問があります。いつ生産して発送になると思いますか?)